Nitrenes are reactive intermediates for many organic reactions, such
as Curtius rearrangement. The thermo- or photochemical- decomposition
of azides or isocyanates was known to generate nitrenes. We investigated
the thermal chemistry of nitrene adsorbed on Cu(111) using benzyl azide
(Bz-N=N=N), benzyl isocyanate (Bz-N=C=O) and phenyl isocyanate
(ph-N=C=O) as precursors under ultrahigh vacuum conditions using
temperature-programmed reaction/desorption (TPR/D), reflectionabsorption
infrared spectroscopy (RAIRS) and X-ray photoelectron
spectroscopy (XPS). Our study shows that despite of the isoelectronic
functionalities (-N=N=N vs. -N=C=O) these molecules undergo different
reaction pathways. For benzyl azide (Bz-N=N=N), the azido group losses
N2 ,and the phenyl group migrates from nitrogen to carbon, forming
surface bound H2C=N-Ph at 210 K. Eventually, H2 elimination and a
carbon-to-nitrogen phenyl shift give the thermally stable ph-CN final
product. XPS reveals that benzyl isocyanate (Bz-N=C=O) rearranges to
form amide intermediate on the surface, which breaks into CO2, HCN
and toluene at 410 K. RAIRs suggests that phenyl isocyanate
(ph-N=C=O) undergoes cyclodimerization, cyclotrimerization and
condensation to remove CO2 at 170 K, and phenyl group shifts from
nitrogen to carbon to produce a metal bound acyl nitrene species
(Ph-(C=O)-N---Cu) at 410 K.
| Identifer | oai:union.ndltd.org:NSYSU/oai:NSYSU:etd-0809111-120608 |
| Date | 09 August 2011 |
| Creators | Ma, Kuo-Chen |
| Contributors | Hsiu-Wei Chen, CHAO-MING CHIANG, Chia C. Wang |
| Publisher | NSYSU |
| Source Sets | NSYSU Electronic Thesis and Dissertation Archive |
| Language | Cholon |
| Detected Language | English |
| Type | text |
| Format | application/pdf |
| Source | http://etd.lib.nsysu.edu.tw/ETD-db/ETD-search/view_etd?URN=etd-0809111-120608 |
| Rights | user_define, Copyright information available at source archive |
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